1. Field of the Invention
The present invention relates to sanitary fixtures having a reservoir and a deck on one side of the reservoir, and a process for molding involving the use of an extended deck insert attached to a mold.
2. Background of the Related Art
In the development of bathtubs, porcelain-cast iron fixtures have gradually been replaced by lighter and more resilient composite structures. One of the difficulties with the porcelain-cast iron and enamelled fixtures has been their susceptibility to impact damage and their extreme weight which makes movement and installation of large fixtures such as bathtubs and whirlpool tubs difficult. The porcelain-cast iron fixtures did have the advantage of having a very solid feel and high weight bearing capability.
Initial attempts by the industry to replace these porcelain-cast iron fixtures proved difficult. The thin stainless steel fixtures were lighter than the porcelain-cast iron fixtures but did not have the solid feel, or structural strength required for large articles such as bathtubs and whirlpool tubs. The early composite structures had a plastic, hollow feel and would deform, crack, chip or delaminate when subjected to impact, thermal shock or the weight of the typical bather. Production of these tubs required the use of a large amount of polymeric material which increased the weight of the tub and increased the cost of manufacture. Furthermore, certain polymeric materials or resins shrink upon curing. This resulted in bowing, warpage, and distortion of the tubs. This problem is especially acute on extended deck portions which are often provided on luxury bathtubs. The shrinkage and bowing of the polymeric material weakens the structural strength of extended decks which must support the weight of the user. Shrinkage and bowing also has resulted in negative drainage, from the deck's surface to the outside wall, leaving pools of water at the edge of the deck.
Commonly assigned U.S. Pat. No. 5,129,804 to Marsilio et al., which is incorporated by reference herein, describes lightweight composite plumbing fixtures, such as bathtubs which have the look, feel and strength of porcelain-cast iron fixtures but not the susceptibility to impact damage and extreme weight of porcelain-cast iron fixtures. These plumbing fixtures are produced in a mold having an apron insert. The apron insert is used to produce a bathtub having an area of reduced thickness in the polymeric material on the non-finish side of the apron. The area of reduced thickness serves to alleviate the problems of distortion, bowing and warpage associated with the shrinkage of polymeric material in the apron portion of the tub. This invention is not concerned with solving the shortcomings of extended deck tubs. Accordingly, when extended decks are provided with such bathtubs, they still suffer from the problems typically associated with shrinkage of the polymeric material. This shrinkage causes negative drainage and weakens the structural strength of the deck.
Commonly assigned U.S. patent application Ser. No. 07/516,284, now abandoned, to Marsilio et al., which is incorporated by reference herein, describes polymeric composite molded structures having a polymeric shell layer, a fiber reinforced resin layer adhered to the non-finish side of the shell. A weight bearing reinforcing structure (such as chip-board) is adhered below the reservoir to the non-finish side of the shell. A plurality of reinforcing wooden planks are placed below the deck portion of the shell. While the planks add some strength and rigidity to the deck, the use of the planks does not solve the problems due to shrinkage of the polymeric material, and does not fully alleviate bowing if used in molding an extended deck bathtub.
Reinforcing grids have been used to add strength and rigidity to the surface of bathtubs. For example, U.S. Pat. No. 2,820,228 describes the reinforcement of a bathtub by a gridwork secured to the bottom of the tub. The gridwork may also extend to the sides of the tub in order to deaden vibrations. Although the gridwork adds strength, it also adds weight, requires additional steps and materials in the manufacturing process and does not strengthen the deck.
The use of ribs to add structural rigidity and reduce weight have been described in the formation of composite structures. For example, U.S. Pat. No. 3,419,457 discloses a sheet having a plurality of ribs which intersect and are united at their respective points of intersection. A sheet, having the ribs, is combined with another sheet to form a composite structure. The composite structure has two layers of reinforced plastic each elevated and separated from the other by the ribs. The ribs add structural rigidity while reducing weight. While the laminated, ribbed structure reduces weight and adds rigidity, it requires additional manufacturing steps and complicates the manufacturing process.
Various patents describe creating cavities in molded articles. For example, U.S. Pat. Nos. 3,610,563, 3,674,394 and 3,368,239 describe methods for forming articles, such as tanks and similar molded hollow articles. During the molding operation, a balloon or tube is expanded in the mold, resulting in the production of a hollow article. The balloons and tubes are not rigid enough to withstand the pressures and high temperatures encountered during the injection molding process. Further, the balloons and tubes would be deformed by the molding material resulting in irregularities in shape, and weakening the structure of the molded object.
German Patent DT 2951091 describes the formation of a plastic bathtub which has parallel tubes extending the length of a flange. The tubes may be filled with foam or other materials. The purpose of the tubes is to add rigidity to the tub and reinforce the structure, taking the place of heavy steel rods, which were formerly used to reinforce the tub. The tubes are only useful in areas having a large cross-section, may be difficult to insert during the molding process and add complexity to the manufacturing operations.
Commonly assigned U.S. Pat. No. 4,664,982 to Genovese et al. and patent application Ser. No. 07/400,289, now abandoned, to Kuszaj et al., both of which are incorporated by reference herein, describe polymeric foam backed enamelled-carbon steel or stainless steel plumbing fixtures that are resistant to chipping, cracking, crazing, delamination or deformation when subjected to impact from either the finish or non-finish side. The use of the aforementioned composite structures results in fixtures which have the feel of porcelain-cast iron and enameled fixtures, high impact strength and resistance to delamination. These composite structures possess excellent physical and mechanical properties as the result of the chemical bonding of the reinforced foamed polymeric layer to the enamelled steel or stainless steel shell. A problem with such fixtures, however, is that a large amount of polymeric material is used in certain portions of the tubs, resulting in increased weight and increased cost. In addition, in the portions having wider cross-sectional areas of polymeric material, the fixtures are subject to problems due to distortion, bow, and warpage from the shrinkage of the polymeric material as it cures. They suffer distortion, bow and warpage in the thicker portions (such as an extended deck portion) due to the inability of the polymeric material to release heat and gas produced during the curing process.
In another process the enamelled-steel shell is replaced with a polymeric-cosmetic surface layer and is bound directly to a foamed plastic substrate to provide a high impact strength delamination-resistant structure. This approach is disclosed in commonly assigned U.S. Pat. Nos. 4,844,944 and 4,844,955, both to Graefe et al., the disclosures of which are incorporated by reference herein. The approach suffers from the same problems described above with regard to U.S. Pat. No. 4,664,982 and application Ser. No. 07/400,289, now abandoned.
Accordingly, none of the related art describes a method for molding fixtures which allows for the reduction of weight and/or thickness of the deck portion of the molded fixture while alleviating the problem of shrinkage of the polymeric material below the deck which causes negative drainage and weakens the structural strength of the deck.
It is, therefore, an object of the present invention to provide a lightweight composite plumbing fixture such as a bathtub which does not suffer from the negative drainage and weakened deck structure problems associated with the shrinkage of polymeric materials.
It is also an object of the present invention to provide an attachment for molding a plumbing fixture such as a bathtub which does not suffer from warpage, bow and negative drainage problems associated with the shrinkage of polymeric materials in deck areas having a relatively large cross-section.